For three billion years, single-celled life ruled supreme on Earth. But how did it begin? Solving this mystery is a major problem in astrobiology, but now scientists think they may be a step closer to an answer.
Electricity, or at least the transfer of electrons, is essential to life on our planet, and in a new experiment scientists have built on an earlier theory to suggest how this might have occurred in the young Earth’s oceans. It had previously been suggested that chimney-shaped hydrothermal vents known as chemical gardens on the seafloor supplied the electricity. The latest research shows that a specific type of these small chimneys may have been key.
In the study, published in the journal Angewandte Chemie International Edition, a team from NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California was able to power an LED (light-emitting diode) lightbulb from alkaline vents, suggesting that they gave an electrical boost to early life on Earth that ultimately allowed it to thrive.
Previous research has focused on chimney-like vents before, but notably only looked at acidic chimneys called “black smokers.” This other type of chimney, an alkaline vent, ranging in size from just inches to tens of feet and made from a porous mineral, is thought to be more likely to have provided the spark for life. Scientists think that these vents could have created an electricity gradient, providing a very small amount of electricity – less than a volt – but enough to affect simple life nearby.
“These chimneys can act like electrical wires on the seafloor,” said Laurie Barge of NASA's JPL, lead author of the study, in a statement. “We're harnessing energy as the first life on Earth might have.”
The researchers’ artificial chimneys were made from iron sulfide and iron hydroxide, which can conduct electrons relatively easily. However, early oceans on Earth would also have been abundant in other materials like nickel, hydrogen and carbon dioxide, so future experiments may aim to replicate the results with the latter materials to see if they may also have played a part.
It has been suggested that similar processes could have taken place in other oceans in the Solar System, such as the subsurface ocean on Jupiter’s moon Europa or even a younger Mars. Finding out just how life on Earth began could therefore be crucial in searching for life elsewhere.